A green tendril of what could be a phytoplankton or sulfur bloom snakes its way south of the Baja California peninsula in this true-color Terra MODIS image acquired July 9, 2002. If this is a phytoplankton bloom, then the color is due to sunlight reflecting off of chlorophyll in the phytoplankton. Phytoplankton are tiny, usually microscopic organisms that use chlorophyll for photosynthesis. If this is a sulfur bloom, then what MODIS sees is result of hydrogen sulfide that oxidized into sulfur gas at the surface of the ocean.Sulfur blooms are produced by anaerobic bacteria on the floor of the ocean. The bacteria feed on dead algae and produce hydrogen sulfide as a waste product. The hydrogen sulfide builds up in the sediments of the ocean floor, eventually accumulating to the point at which it bubbles out of the sediment and rises to the ocean surface. When it reaches the surface, it oxidizes into pure sulfur, which in certain amounts is poisonous to marine life and humans. Sensor: Terra/MODIS. Data Start Date: 7/9/02. Data End Date: 7/9/02.